A deactivation fuse is employed to selectively deactivate a portion of the circuits comprising a semiconductor device. For example, it may be determined during manufacturing that certain circuits, or groups of circuits, are malfunctioning, in which case, the malfunctioning circuits can be deactivated, thereby preserving the utility of the remainder of the circuits in the semiconductor device.
FIG. 1 is a schematic circuit diagram of a conventional semiconductor device having a deactivation fuse. Referring to FIG. 1, the conventional semiconductor device 101 includes a power source pin 111, a ground pin 121, a switching clement 131, a resistor 141, a deactivation fuse element 151, an inverter 161 and an internal circuit 171. The switching element 131 is used for opening the deactivation fuse 151. In other words, if the switching element 131 is activated by a control signal C, power supply voltage Vdd is applied to the deactivation fuse 151 through the power source pin 111, thereby supplying high current, which opens the fuse 151 so that it no longer conducts, causing voltage Vo to be driven to a low state, thereby disabling internal circuit 171.
In FIG. 1, assuming that the deactivation fuse 151 is conducting, with power supply voltage Vdd applied to the resistor 141, the input voltage of the inverter 161 remains at a ground voltage (GND) level. Thus, the output Vo of the inverter 161 is driven to a high logic level. If the fuse 151 is opened, then if the power supply voltage Vdd is applied to the resistor 141, the input voltage of the inverter 161 rises to the power supply voltage (Vdd) level. Thus, the output voltage Vo of the inverter 161 is driven to a logic low level. In other words, the output of the inverter 161 changes according to the conducting state of the fuse 151.
In the conventional semiconductor device 101, current flows through the resistor 141 so long as the power supply voltage Vdd is applied to the resistor 141, whether the fuse 151 is opened or closed. This amounts to unnecessary power consumption by the semiconductor device 101.